Meilah 4:4-5

Meilah 4:4

Piggul and nosar don’t combine with one another because they are from two different categories. Creeping things and neveila, and for that matter, neveila and flesh from a corpse, don’t combine with one another to transmit ritual impurity, not even of the lesser type of impurity. Food that was rendered ritually impure through contact with a primary source does combine with food that was rendered impure through a secondary source in order to convey the lesser form of ritual impurity.

Meilah 4:5

All foods combine to form the volume of half a pras to transmit impurity by eating [a pras is half a loaf when a kav of wheat is used to make three such loaves, so half a pras is a quarter-loaf], to compose the food for two meals used in creating an eruv techumin (to shift one’s Shabbos boundary), to form the volume of an egg that transmits ritual impurity to food, to form the volume of a dried fig vis-à-vis carrying on Shabbos and to form the volume of a date vis-à-vis eating on Yom Kippur. All beverages combine to form up a reviis (about 3 ounces) in order to transmit impurity by drinking and to form a (prohibited) mouthful on Yom Kippur.